1. Field of the Invention
The invention relates to a control system for a hybrid electric vehicle powertrain having an engine and an electric motor with either a parallel or a series power flow path.
2. Background Art
Powertrains for known hybrid electric vehicles include an internal combustion engine, which functions as a first power source, and a high voltage induction motor with a battery, which function as a second power source. The power sources may be part of a powertrain with parallel power flow paths or a series power flow path. In parallel hybrid powertrains, an engine, a motor, a generator and a battery, together with gearing, define a first power delivery configuration. A second power delivery configuration comprises only the motor, the generator and the battery, together with gearing.
The generator in a parallel hybrid powertrain is driven by the engine in a first mechanical power flow path that is established between the engine and the transmission torque output shaft. A second power flow path is an electrical power flow path, which distributes power from the engine to the generator, the latter driving the torque output shaft through the gearing. With the generator and the motor operating in this configuration, they together establish a continuously variable ratio, electromechanical transmission system.
A fully mechanical power flow path can be established by braking the generator as engine power is transmitted with a fixed gear ratio through the gearing.
A hybrid powertrain with a series power flow path includes an engine mechanically connected to a generator, an electric motor electrically coupled to the generator, and torque output gearing mechanically connected to the motor.
A powertrain comprising the present invention has features that are common to the features of the hybrid electric vehicle powertrain disclosed in the co-pending patent application identified above, which is assigned to the Assignee of the present invention. Reference may be made to that co-pending application for the purpose of supplementing this disclosure. The disclosure of the co-pending application is incorporated in this disclosure by reference.